1. Technical Field
The present disclosure generally relates to mobile telecommunication devices equipped with a near field communication circuit (NFC).
2. Discussion of the Related Art
Cell phones are more and more often equipped with a near field communication interface, which enables combining electromagnetic transponder functions with mobile telephony functions. In particular, this adds contactless card type electromagnetic transponder emulation functions to the mobile telecommunication device, of personal digital assistant, cell phone, smartphone, or other type. This enriches the features of the mobile device, which can then be used, for example, as an electronic purse, as a debit or credit system, as an access validation device, as a transport ticket, etc.
To emulate the operation of a contactless chip card, the mobile telecommunication device is equipped with a contactless front-end integrated circuit (CLF), also called an NFC router. This router is equipped with a radio frequency transceiver front head associated with a low-range antenna to communicate like an electromagnetic transponder. The router uses the capacities of the mobile device processor(s) for data processing and storage operations. For access control, electronic purse, payment, and other applications, a secure element enabling to authenticate the user is used. This secure element is either integrated to the mobile telecommunication device (dedicated integrated circuit, circuit welded to the printed circuit board) or contained in a microcircuit supported by a subscriber identification module (SIM), or any other removable card, for example in the standard format of a memory card.
A specificity of such a mobile telecommunication device is that it is capable of operating in NFC when it is off or, more generally, when its circuits are not powered by the battery or another power supply element of the mobile device.
In this case, the NFC router draws the power necessary to its operation, like an electromagnetic transponder, from the field radiated by a nearby terminal. It then provides the power supply necessary to the security module circuits to validate near-field transactions.
When the device is powered by its battery and its internal circuits are operating, different security mechanisms may be implemented, for example, to avoid a hacking of the SIM card. However, when the device is only powered via the NFC router, such mechanisms may be difficult to implement. This is a weakness of such a mobile telecommunication device.